The present invention relates to a device for controlling impressional force, particularly in offset printing machines. The devices are intended for lifting in impression cylinders and their throw-off. Furthermore, the device can be used for controlling further steps of the printing machine, e.g. for controlling the inking rollers of the inking mechanism and for damping, i.e. their lifting in and their throw-off.
One of the devices hitherto known is controlled manually by means of a control lever. The mechanism of that device consists of a multi-arm lever, which is adjusted by means of a cam, a system of tie rods and a coupling link, provided with two projections. This device operates in such manner, that the offset roller is approached and withdrawn from the form roller and the impression cylinder, thus lifting in the said cylinders into imprinting force. The throw-off is derived from the disengaging roller on the pressure cylinder via a disengaging link, mechanically.
The disadvantage of this device consists in that it does not make possible a connection with electrical control elements. A further disadvantage consists in that an incorrect pulse cannot be corrected and that, upon starting a duty cycle, a self-retaining interval is necessary upon slight turning of the engaging link, for insuring that the engaging link does not return into its initial position, thus preventing the start of the duty cycle.
Another known device controls the impression cylinders by electromagnets. The mechanism of this device is arranged in such manner, that a two arm level is used for each step that is required. All two arm levers are adjusted by means of a cam. The duty cycle is controlled by a control link, which is provided with a control pin and a control recess.
The disadvantage of this device consists in that an incorrect pulse cannot be corrected, and for starting a duty cycle, a self-retaining interval is necessary upon slight turning of the control link. This self-retaining interval insures that the control link does not return into its initial position, whereby the possibility of preventing the start of the duty cycle is removed.